Reaction of phosphoric acid, urea, and ammonia

ABSTRACT

A process for obtaining, in the same manufacturing process, two different fertilizers, namely a solid or liquid fertilizer which is based on ammonium and urea polyphosphate and the solutions of which are clear and stable over a period of time, and a solid binary fertilizer (N,P) or solid ternary fertilizer (N, P, K) which is very concentrated and based on ammonium-urea phosphate. The process of the invention makes use of the action of ammoniation and condensation of urea phosphate, because owing to its mode of formation this compound gives rise to a separation of the impurities of wet process orthophosphoric acid, e.g., iron, aluminum, calcium, magnesia and fluorine, which remain in the mother liquors from centrifugation of the urea phosphate crystals. According to a preferred embodiment of the invention a reaction product is obtained which is constituted mainly of ammonium pyrophosphate. The non-ortho P2O5/ total P2O5 ratio of the product obtained is generally from 50 to 70 percent, but such high values as 92-98 percent have also been obtained in certain embodiments according to the invention. The process of the invention combines the chemical reactions between phosphoric acid, urea, and ammonia in such a manner that the overall thermal balance provides an excess, thus making it possible to operate under autothermal conditions.

1451 Jan 30, 1973 [54] REACTION OF PHOSPI-IORIC ACID,

UREA, AND AMMONIA [75] Inventor? MarcelGittenait,Colombes, France [73]Assignee: Societe Anonyme: Ugine Kuhlmann,

Paris, France [22] Filed: Dec. 28, 1970 [21] Appl. No.: 101,962

[30] Foreign Application Priority Data Jan. 9, 1970 France ..7000806July 7, 1970 France ..7025133 [52] ;U.S.Cl. .....7l/29,23/107, 71/35[51] Int. Cl. ..C05b 7/00 [58] Field ofSearch ..71/29, 34, 35,43;23/106A, 23/107 [56] References Cited 1.77% MM UNITED STATES PATENTS 3,397,0358/1968 Yu Shen et al ..23/106 3,540,874 11/1970 Stinson i ..71/293,419,349 12/1968 Rohlfs et al..... 73/107 R 3,333,921 8/1967Krellmueller ..23/106 3,495,937 2/1970 Yu Shen et a1 ..23/106 3,586,4956/1971 Bauwens et a1 ..71/29 FOREIGN PATENTS oiz APPLICATIONS- l,l49,9244/1969 Great Britain ..71/29 Primary Examiner- Reuben Friedman AssistantExaminer- Richard Barnes A ttomey- Hammond & Littell [57] ABSTRACT Aprocess for obtaining, in the same manufacturing process, two differentfertilizers, namely a solid or liquid fertilizer which is based onammonium and urea polyphosphate and the solutions of which are clear andstable over a period of time, and a solid binary fertilizer (N,P) orsolid ternary fertilizer (N, P, K) which is very concentrated and basedon ammoniumurea phosphate.

The process of the invention makes use of the action of ammoniation andcondensation of urea phosphate, because owing to its mode of formationthis compound gives rise to a separation of the impurities of wetprocess orthophosphoric acid, e.g., iron, aluminum, calcium, magnesiaand fluorine, which remain in the mother liquors from centrifugation ofthe urea phosphate crystals.

According to a preferred embodiment of the invention a reaction productis obtained which is constituted mainly of ammonium pyrophosphate. Thenon-ortho P O total P 0 ratio of the product obtained is generally from50 to 70 percent, but such high values as 9298 percent have also beenobtained in certain embodiments according to the invention.

The process of the invention combines the chemical reactions betweenphosphoric acid, urea, and ammonia in such a manner that the overallthermal balance provides an excess, thus making it possible to operateunder autothermal conditions.

14 Claims, 1 Drawing Figure PAIENIEUJAHMB 3.713.802

1a 4 1+ 5 ij MARCEL GITTENAIT, Inventor HAMMOND &: LITIELL, AttorneysThe present invention has as object a process for the obtaining of newreaction products of wet process phosphoric acid, urea, and ammonia. Itrelates more particularly to the manufacture of solid and/or liquidfertilizers based on ammonium and urea polyphosphates by a process whichcan be carried out under autothermic conditions and which in additionmakes it possible to obtain, in the same manufacturing process, solidbinary or ternary fertilizer based on ammonium and urea phosphate.

The invention relates more particularly to the liquid and solidfertilizers obtained by the process described, which have high contentsof fertilizing elements and which, when presented in solid form, may beutilized in that form by spreading or, after dissolving, in water, byspraying, injection, sprinkling, or dilution in the same manners asliquid fertilizers.

The manufacture of solid fertilizers capable of being formed intosolutions or suspensions is known.

As a document illustrating the prior art in this field mention may bemade of French Pat. No. 1,519,801, which describes fertilizers insuspension form obtained by adding water to solid fertilizers based onammonium phosphate, urea, and potassium chloride.

It is found necessary to be able to offer users not only fertilizers insuspension form but also liquid fertilizers which have a high aconcentration as that of fertilizers in suspension form, for examplethose described in French Pat. No. 1,519,801, and which are neverthelesslimpid and stable over a period of time.

In this connection it is known that fertilizers based on ammoniumpolyphosphate are more soluble in water than fertilizers based onammonium orthophosphate and that consequently they are more suitable forliquid formulations.

Numerous documents exist which illustrate the prior art in connectionwith the manufacture of ammonium polyphosphates. For the most part theserelate to processes employing thermal treatment of the products ofammoniation of orthophosphoric acid produced by the furnace or wetprocesses, the neutralization of polyphosphoric acids by ammonia, orelse the thermal condensation of mono-and/or di-ammonium phosphates.

Other previous documents relate to processes for the manufacture ofammonium polyphosphate by thermal treatment of ammoniated phosphoricacid ro monoand/or di-ammonium phosphates with urea, which serves ascondensation agent.

French Pat. Nos. 1,533,272 and 1,575,795, for example, relate toprocesses utilizing the last-mentioned technique but necessitatingprevious partial purification of the orthophosphoric acid used; inaddition although the process described in French Pat. No. 1,533,272, isautothermal, the process corresponding to French Pat. No. 1,575,795requires heat to be supplied from an external source.

British Pat. No. 1,149,924 describes for the production of crystallizedurea phosphate by reacting urea and phosphoric acid. French Pat. No.1,481,286 also relates to a process for the production of an ammoniumpolyphosphate by neutralizing phosphoric acid with urea. In order toillustrate the prior art still further,

2 mention may be made of U.S. Pat. No. 3,022,153

which proposes the direct use of wet process phosphoric acid, urea, andammonia, with the conversion of the phosphoric acid into urea phosphateand subsequent ammoniation of the latter. U.S. Pat. No. 3,022,153proposes more specifically the complexing by means of glycerin ofphosphates which are insoluble in the liquid reaction medium, and thesubsequent addition of an amine to the reaction product in order toobtain good keeping properties.

French Pat. Nos. 1,411,254, 1,461,027, and 1,471,510 describe the use ofurea and also urea phosphate as condensation and ammoniation agents forthe purpose of producing more or less water-soluble ammoniumpolyphosphates which are intended more particularly for use asinflammation inhibitors for plastics materials, textiles, and paints.The thermal condensation is effected either at temperatures between 170Cand 260C or at temperatures between 200 and 300C in the presence of anadditive composed of an ammonium polyphosphate having a clearlydetermined crystalline form, or else at temperatures between and 350C inan atmosphere controlled for ammonia vapor and water vapor pressure, inorder to obtain a polyphosphate possessing previously selectedsolubility in water. All these processes for the manufacture of ammoniumpolyphosphate require very considerable consumption of heat to enablethem to be carried out.

The same is true of the processes described in French Pat. No. 1,437,486and German Pat. Nos. 1,216,856 and 1,228,593 which likewise use urea andurea phosphate as condensation agents in the preparation of chainpolyphosphates applying thermal conditions between 1 10C and 400C, butwith a very long heating time, amounting, to from 2 to 3 hours.

Among all the processes described in the earlier patents mentionedabove, those which do not have the particular object of producingammonium polyphosphates for the manufacture of liquid fertilizers do notspecify the previous purification of the raw materials. This operation,which is mentioned in. French Pat. Nos. 1,533,272 and 1,575,795 isnevertheless necessary since otherwise the liquors obtained are notstable over a period of time, and an insoluble product is formed whichin the course of time is deposited in the storage vessels. lt istherefore desirable to develop a process which makes it possible toobtain ammonium polyphosphates suitable for the manufacture offertilizers and which eliminates the need for previous purification ofthe raw materials, particularly phosphoric acid. i

The invention has as its first object a process for the obtaining ofproducts based on ammonium-urea polyphosphate which can be carried outwithout supplying heat, under autothermal conditions.

The invention also has as object a process for the manufacture offertilizers based on ammonium polyphosphates which provide the advantageover orthophosphates of being more soluble, so that they" provide highlyconcentrated liquid fertilizers, and of possessing a complexing power inrelation to Fe, Al, Ca, Mg and certain other ions so as to provide clearsolutions which will keep.

The invention has yet as another object a process for obtaining solidfertilizers or liquid fertilizers which are 'which'use is made of thecrystallization of the urea phosphate produced by contacting phosphoricacid with urea, with the separation of impurities such as iron,aluminum, calcium, fluorine and magnesium which remain in the motherliquors from the crystals centrifugation.

The invention has as a further object a process in which the motherliquors remaining from the crystallization of the urea phosphate andcontaining all the impurities originating from the phosphatic rock (Fe,Al, Ca, Mg, F, etc.) are likewise converted into a concentrated binaryor ternary fertilizer based on ammonium-urea phosphate.

The invention has as another object a process for obtaining, in the samemanufacturing process, two different fertilizers, namely a solid orliquid fertilizer which is based on ammonium and urea polyphosphate andthe. solutions of which are clear and stable over a the fertilizercomponents N:P,0 is higher than 0.5 and in particular is between 0.52and 0.55. The invention likewise has as object a process for theproduction of mainly of ammonium pyrophosphate. The non-ortho stableliquid fertilizers in which the weight ratio of the fertilizercomponents N:P 0 is lower than0l5 and in particular is between 0.43 and0.49.

The inventionhas as another object a possess in which the startingmaterial is a non-concentrated wet process phosphoric acid and in whichan ammonium polyphosphategbased fertilizer is obtained with a low degreeof condensation (principally ammonium pyrophosphate), this fertilizerconsequently being highly soluble in water.

The invention therefore relates to a process for obtaining new reactionproducts of phosphoric acid, urea, and ammonia by converting phosphoricacid into urea phosphate and subsequent ammoniation of the latter, saidprocess being characterized in that (l) the urea and the unpurified wetprocess phosphoric acid, titratingat 30-60 percent P 0 are directlyreacted, thereby obtaining a urea phosphate which crystallizes and asolution which contains practically all the mineral impurities of thephosphoric acid and which can be utilized in a subsequent operation, and(2) at least one treatment of said urea phosphate with ammonia is ef--fected, at'a pressure at least equal to atmospheric pressure, thusfinally obtaining an ammoniated polyphosphate product havinga low degreeof condensation and consisting of an ammonium p olyphosphate thenonortho T30 content of which constitutes at least percent of its totalP 0 content, the combination of the reactions carried out in stages (I)and (2) leading.

tothermic conditions. i

The process of the invention makes use of the action of ammoniation andcondensation of urea phosphate, because owing to its mode of formationthis compound gives rise to a separation of the impurities of wetprocess orthophosphoric acid, e.g. iron, aluminum, calcium, magnesia andfluorine, which remain in the mother liquors form centrifugation of theurea phosphate crystals.

According to a preferred embodiment of the inven-' tion a reactionproduct is obtained which is constituted P 0 total P 0 ratio of the,product obtained is generally from 50 to percent, but such high valuesas 92-98 percent have also been obtained in certain embodimentsaccording to the invention.

The process of the invention combines the chemical reactions betweenphosphoric acid, urea, and ammonia in such a manner that the overallthermal balance provides an excess, thus making it possible to operateunder authotherm al conditions.

It is known that urea phosphate is an addition compound which inchemical reactions behaves like a mixture of phosphoric acid and urea.When this productis ammoniated, depending on the degree of ammoniationand the temperature at which the operation is carried out, the followingreactions may, occur partially or totally:

The reactions of ammoniation of ortho-and pyrophosphoric acids arehighly exothermic, while the reactions of decomposition of urea andpolymerization of the phosphate molecule are endothermic.

According to the teaching of the invention, the overall calorificbalance of theprocess is positive when the reaction is limited to theless condensed forms of ammonium p'olyphosphate and essentially toammonium pyrophosphate.

The process of the invention is verysuitable for continuous operationand it will be illustrated below with reference to the.accompanyingdrawing,'which illustrates'diagrammatically an apparatus for thecontinuous manufacture of liquid fertilizer by ammoniation of ureaphosphate. It is nevertheless obvious that the process may be carriedout discontinuously, even in a single vessel.

Before illustrating the inventionby detailed examples of itsperformance, some general information will be given regarding a mode ofperformance which may advantageously be used in practice.

Wet process phosphoric acid, with a concentration between 30 and 60.percent P 0 and urea in the solid state or in the form of a concentratedsolution, coming from a factory producing urea, is introduced into avessel provided with an agitation device. After agitating for a shortperiod, the urea phosphate crystallizes and it is separated bycentrifugation from the residual mother liquors, which retain theimpurities of the wet process phosphoric acid.

The urea phosphate is then introduced into a container in which it isammoniated at atmospheric pressure or under a higher pressure until theproduct passes from the solid to the liquid state through the action ofthe heat released by the partial neutralization of the phosphoric acid.The product becomes pasty at 80C and liquid at 8590C, whereas themelting temperature of non-ammoniated urea phosphate prepared from wetprocess phosphoric acid is 113C.

The ammoniated liquid product is the introduced into below. reactiontube of small diameter, at the inlet of which it undergoes supplementaryammoniation by means of an ammonia injector. Inside this tube thereactions of decomposition of urea, condensation of the phosphatemolecule, and neutralization of the orthoand polyphosphoric acids takeplace. The temperature of the products which is 110C on entering thereaction tube, rises to 155C at the outlet. The product obtained has afrothy appearance and, depending on whether it is intended for theproduction of solid fertilizer or the production of liquid fertilizer,it is treated differently as described below,

In the case of the manufacture of a solid fertilizer, the product isvigorously kneaded before being introduced into a granulation plant, soas to assist the crystallization of the polyphosphate and the obtainingof hard granules.

The product obtained is a mixture of ammonium orth ophosphate, ammoniumpolyphosphate, and urea, and has a total P content of 45-47 percent, ofwhich 53-67 percent are in polyphosphoric form, and a total N content of23-25 percent, of which 10.5- percent is ammoniacal nitrogen.

The amount of decomposed urea, which serves as condensation andammoniation agent, is usually from 40 to 45 percent of the urea used.

During granulation it is possible to add other fertilizing materials,such as for example additional urea in order to obtain a binaryfertilizer titrating at 30 percent N, 30 percent P 0 or else potassiumchloride in order to obtain a ternary fertilizer titrating at percent N,20 percent P 0 20 percent K 0.

' When the product is intended for the manufacture of liquidfertilizers, the foams leaving the reaction tube are collected in adissolution vessel, to which the water necessary to obtain the desiredtitre is added.

The liquid fertilizer is cooled by passing through a cooler and recycledto the dissolution vessel so as to maintain a temperature of -60C in thelatter. Liquid fertilizers titrating at 15-17 percent N and 27-31percent P 0, can be obtained in thismanner. 1n the practical performanceof a process of this kind the weight ratio NzP generally varies between0.52 and 0.55 in the liquors obtained.

For. certain fertilizing treatments it is desirable to have availableliquid fertilizers in which the N130 weight ratio'is lower than 0.5' andmore particularly between 0.43 and 0.49.

According to a first means, the reduction of the N:P,O weight ratio inthe polyphosphate liquors treated may be effected byaddiurea-ammoniumtionally introducing wet process phosphoric acid intosaid liquors.

The required proportion of wet process phosphoric acid may be introducedin this way into the urea phosphate undergoing ammoniation andcondensation and/or into the zone of dissolution of theurea-ammonium-polyphosphate foams leaving the reaction zone. If desired,the M ratio of the liquor may be further adjusted by introducing asmalladditional amount of ammonia. In this embodiment of the inventionit is sufficient to provide simply an additional connection for theintroduction of wetprocess phosphoric acid into the actual ammoniationzone and/or into the dissolution zone.

By this means there havev thus been obtained ureaammonium polyphosphateliquors having a content of l4-l4.6 percent by weight of nitrogen and29.830 percent by weight of P 0 According to another means, which may beused to replace or to supplement the addition of wet process phosphoricacid, the liquors obtained by the process of the invention are cooled;suitable cooling temperatures may be lower than -5C and particularly/ofthe order of -10tolSC.

The N:P O ratio may in fact be lowered to a value below 0.50 by removingureic nitrogen from the ureaammonium polyphosphate liquor obtained bythe process of the invention, by cooling to a temperature of the order10 to -l5C. Urea crystals are formed which, after separation bycentrifugation, leave an urea-ammonium polyphosphate liquor containingby weight 13.6-14 percent N and 31-32% P 0 This liquor is perfectlyclear and almost colorless while the urea crystals separated may bereused for production purposes.

These liquid fertilizers are better balanced from the point of view ofdistribution of fertilizing elements than the solutions based onpolyphosphates which are at present marketed. Oligo elements orinsecticides may also be introduced into these liquid fertilizers, inorder to carry out mixed agricultural treatments when desired.

The mother liquors obtained on the separation of the urea phosphatecrystals are solutions which are saturated at the centrifugationtemperature. They contain all the impurities originating from the wetprocess phosphoric acid and have a water content which,depending on thecentrifugation temperature, varies, for example, from 27 to 45 percentif centrifugation is effected at temperatures between 50 and 18C.Depend.-

ing on their water content, these mother liquors are either ammoniateddirectly or ammoniated after concentration and then introduced into 'aconventional granulation installation for the production of a binaryurea-ammonium phosphate fertilizer or, after addition of otheringredients, of a highly concentrated ternary fertilizer.

It is thus possible to obtain a binary fertilizer titrating at 24.77% N,36.82% P 0 and, after potassium chloride, a ternary fertilizer titratingat 19% B, 19% P 0 19% K 0, as will be illustrated below by Example 1.

The relative-proportion of the two grades of fertilizer, namely solid ofliquid fertilizer based on urea-ammonium polyphosphate and solidfertilizer based on urea-ammonium phosphate obtained in the samemanufacturing cycle, depends on the water content of the startingphosphoric acid, where applicable that of the urea when the latter isintroduced in the form of a solution and on the temperature at which thecrystallized urea phosphate is centrifugated. These various factors canthus be utilized to adjust the relative quantities of fertilizers whichcan be obtained by the process.

The performance of the process of the invention will now be illustrated,without limiting it in any way, by the following examples.

EXAMPLE 1 One-hundred-sixty-five kg of phosphoric acid containing 53.5%P (originating from a wet process phosphoric acid factory) and 74.50 kgof urea containing 46% N are introduced into a vessel equipped with anagitation device.

The temperature of the acid, which was originally from 40 to 43C, dropsby a few degrees after the introduction of the urea and then rises toabout 60C in proportion to the formation of urea phosphate crystals.

The reaction is very rapid and after agitation for 1 hour the crystalsformed are centrifugated and washed in a centrifuge.

The temperature at which'the centrifugation is effected is 50C.

One-hundred-one kg of slightly wet urea phosphate crystals and 138 kg ofmother liquors are obtained.

The crystallized urea phosphate titrates at 44% P 0 and 17.4% N. Themother liquors titrate at 31.5% P 0 and 12.2% N, and contain all theimpurities introduced by the wet process phosphoric acid used.

The crystallized urea phosphate isintroduced into an apparatus which isdiagrammatically illustrated in the accompanying drawing and which willnow be described.

The apparatus comprises a charging hopper '1 for the urea phosphate. Aworm 2 at the foot of the hopper enables the urea phosphate to beintroduced continuously into an ammoniation vessel 3 equipped with anagitator 4. The vessel 3 is in communication with another,. cylindricalcontainer 5, equipped with an agitator 6, through a reaction tube 7 ofsmall section. An overflowpipe 8 also connects the top part of thevessel 3 to the vessel 5.

The agitation device 4, of the first vessel 3, into which thecrystallized phosphate is introduced, is hollow in order to permit theintroduction of gaseous ammonia through the connection9.

A second introduction of ammonia is effected through an injectorl0'discharging into the inlet of the reaction tube 7. The other end ofsaid tube 7 penetrates into the top portion of the second vessel 5, theagitation device 6 of which is equipped with blades6a having a specialprofile for heating foams.

The entire apparatus is heat-insulated when it is desired to manufacturea very solid urea-ammonium polyphosphate.

When it is desired to obtain a liquid fertilizer directly, the secondvessel 5 is a dissolution vessel provided with a water inlet (pipe) 11,a small column 12 for absorbing the gases released, optionally an inletfor ammonia to regulate the pH, a connection 13 for the discharge ofgases, and a recycling pump 14. The

and returns it to the top of the vessel through the pipe recycling pump14 continuously withdraws liquid fertilizer at the bottom of the vessel5 through the pipe l5 17 after having passed it through an externalcooler 16 and the small gas absorption column 12. The product, i.e.,liquid fertilizer, is taken from the circuit through thepipe 18 to bedelivered to storage.

This apparatus is started up by introducing into the ammoniation vessel3 urea phosphate coming from a previous operation and gaseous ammonia soas to form a liquid starting layer at the temperature of -90C.

-When it is considered that the height of the starting layer issufficient, the temperature is allowed to rise to C and the apparatus isthen ready for continuous operation.

The 101 kg of centrifugated phosphate previously obtained are introducedby utilizing a suitable continuous distributor with a flow regulated bythe tempera ture in the liquid mass, this temperature being kept atabout 110C because of the exothermic ammoniation reaction.

At the same time, gaseous ammonia is introduced both-through the hollowagitation device 4 of the ammoniation vessel 3 and through the ammoniainjector 10 situated at the inlet of the reaction tube 7. At the outletof said tube the product flows at a temperature of C into the secondvessel 5. The temperatures are kept stable at 110C in the ammoniationvessel 3 and at 155C at the outlet of the reaction tube 7 throughout theentire operation.

A total of 9.5 kg of gaseous ammonia is introduced and 97 kg ofurea-ammonium polyphosphate are obtained, which after cooling titratesas follows:

total P 0 45.67%

pyro P 0 30.58%

ortho P 0 14.81%

total N 24.80%

ammoniacal N 14.94%

ureic N 9.86%

This product may be granulated in the condition in which it is produced,applying the various conventional granulation techniques such as thosealready describe connection with the granulation of solidpolyphosphates;

The urea-ammonium polyphosphate leaving the reaction tube 7 may also beimmediately dissolved by adding the amount of water necessary forobtaining a liquid fertilizer. Thus,- by adding 53 kg of water to thedissolution vessel 5 there are obtained 150 kg of liquid fertilizertitrating at 16.5% N and 30% P 0 ln cold weather and for storage over along period of time it is preferable to increase the amount of water to68 kg in order to obtain kg of liquid fertilizer titrating at 15% N and27% P 0 The mother liquors, amounting to 138 kg, originating from thecentrifugation of the urea phosphate are ammoniated with 15 kg ofgaseous ammonia. A past having a temperature of l 15C is obtained whichcontains between 15 and 17 percent water depending on the speed at whichthe ammoniation is conducted.

The paste is delivered to a conventional granulation installation inwhich a recycling rate of the order of twice the weight of marketableproduct is maintained.

One-hundred-seventeen kg of granulated binary fertilizer are thusobtained with the following titration:

total N 24.77%

ureic N: 12.82%

ammoniacal N 11.95%

'total P 36.82%

water soluble P 0 citrate 36.16%

water soluble P 0 34.96%

humidity 1.76%

As an alternative, urea and potassium chloride were also added duringthe granulation and a ternary fertilizer was obtained which contained19% N, 19% P 0 and 19% K 0 EXAMPLE 2 107.5 kg of wet process phosphoricacid containing 52.3% P 0 and 181 kg of recycled mother liquors comingfrom a previous operation of centrifugation urea phosphate crystals, ata temperature of 18C, are introduced into a vessel equipped with anagitation device. The mother liquors have a P 0 content of 21.47 percentand contain 8.82 percent of ureic N.

After homogenization by agitation of the mixture of phosphoric acid andmother liquors 47.5 kg of solid urea containing 46% N is added thereto.The temperature drops a few degrees as the result of the dissolution ofthe urea and then rises by about 12C in proportion to thecrystallization of the urea phosphate.

The paste obtained, with the crystals in suspension, is cooled to about118C and the crystals are then separated by centrifuging.

One-hundred kg' of urea phosphate crystals and 136 kg of mother liquorsare obtained, which corresponds to a crystallization yield of 79percent.

Analyses of the crystals and mother liquors give the following contents:

Crystals Mother liquors P,O,% 44.40 21.47 N% 17.35 8.82 F% 0.07 0.70 Mg%0.0215 0.2890 Fe% 0.0725 1.1500 A1% 0.0400 0.3700 Ca% 0.0023 0.0407 Si%0.0100 0.0300

impurities, are concentrated from a P 0 content of Y EXAMPLE 3 In thisexample the total amount (97 kg) of urea-ammonium polyphosphate obtainedin accordance with Example 1 at the outlet of the reaction tube 7 istreated. This quantity is dissolved in the vessel by introducing intothis dissolution vessel 68 kg of water, 25 kg of wet process phosphoricacid containing 53.5 percent of P 0 and 4 kg of additional ammonia.There are finally obtained 194 kg of urea-ammonium polyphosphate liquorcontaining 14% N and 30% P 0 The weight ratio N: P 0 of this liquor is0.466.

EXAMPLE 4 An urea-ammonium polyphosphate liquor obtained in accordancewith the process indicated in Example 1 and titrating on analysis at 16%N and 29.5% N and 29.5% P 0 is subjected to a temperature of l5C forabout 10 minutes so as to allow part of the urea to crystallize. Afterseparation of this part by centrifuging, the centrifuged liquor has atitre of 13.7% N and It is found that the weight ratio N:P O whichwas0.53 in the original liquor, has fallen to 0.43 in the centrifugedliquor.

1 claim:

1. A process for the production of reaction products of phosphoric acid,urea, and ammonia by the conversion of phosphoric acid into ureaphosphate and subsequent ammoniation of the urea phosphate, this processincluding stages in which: (1) urea and unpurified wet processphosphoric acid containing 30-60% of P 0 are reacted directly with theformation of a, urea phosphate, the urea phosphate crystallizing out andleaving in solution mineral impurities accompanying the phosphoric acid;and (2) at least one treatment of said urea phosphate with ammonia iscarried out at a pressure at least equal to atmospheric pressure, thesaid at least one treatment with ammonia leading to the formation of anammoniated polyphosphate product having a low degree of condensation andconsisting of an ammonium polyphosphate the non-ortho P 0 content ofwhich constitutes at least 50 percent of its total P 0 content; thecombination of the reactions carried out in stages l and (2) providingan overall excess of heat.

2. A process as claimed in claim 1, wherein the urea reactant isselected from the group consisting of solid urea and concentratedsolutions of urea.

3. A process as claimed inclaim 1, wherein the ammonia reactant isselected from consisting of ammonia and liquid ammonia.

4. A process as claimed in claim 1, wherein the ammonium polyphosphateis principally ammonium pyrophosphate and the at least one treatmentwith ammonia is carried out at a temperature between and C.

5. A process as claimed in claim 4 wherein the process is operated underautothermic conditions.

6. A process as claimed in claim 1, wherein the said at least onetreatment with ammonia leads to the formation of a product the non-orthoP content of which is from 50-70 percent of its total P 0 content.

7. A process as claimed in claim 1, wherein an ureaammoniumpolyphosphate based fertilizer is obtained by the addition, after thecrystallization of urea phosphate and subsequent ammoniation thereof, ofan amount of urea-leading to the production of a solid binary fertilizercontaining about 3% N and 30% P 0 8. A process as claimed in claim 7,wherein, by the addition also of potassium chloride, the product ismodified to provide a solid ternary fertilizer containing about 20% N,20% P 0 20% k O.

9. A process as claimed in claim 1, wherein'a liquid fertilizer isobtained by dissolving the urea-ammonium polyphosphate formed in stage(2) in water, whereby a liquid fertilizer containing about 15 to 17% Nand 27to 31% P 0 is provided.

10. A process as claimed in claim 1, wherein a liquid fertilizer isobtained by dissolving the urea-ammonium polyphosphate formed in stage(2) in water, and cooling the liquors obtained after dissolving theurea-ammonium polyphosphate in water to a temperature lower than -5C.

11. A process as claimed in claim 1 wherein a liquid fertilizer isobtained by dissolving the urea-ammonium polyphosphate formed in stage(2) in water and introducing wet process phosphoric acidin the zone inwhich the urea-ammonium polyphosphate is dissolved. V

P 0 is produced by the granulation of material comprising the paste.

14. A process as claimed in claim 13, wherein potassium chloride andurea are added to the paste, whereby, after granulation, a solidternaryfertilizer containing about 19% N, 19% P 0 and 19% K 0 is produced.

1. A process for the production of reaction products of phosphoric acid,urea, and ammonia by the conversion of phosphoric acid into ureaphosphate and subsequent ammoniation of the urea phosphate, this processincluding stages in which: (1) urea and unpurified wet processphosphoric acid containing 30-60% of P2O5 are reacted directly with theformation of a urea phosphate, the urea phosphate crystallizing out andleaving in solution mineral impurities accompanying the phosphoric acid;and (2) at least one treatment of said urea phosphate with ammonia iscarried out at a pressure at least equal to atmospheric pressure, thesaid at least one treatment with ammonia leading to the formation of anammoniated polyphosphate product having a low degree of condensation andconsisting of an ammonium polyphosphate the non-ortho P2O5 content ofwhich constitutes at least 50 percent of its total P2O5 content; thecombination of the reactions carried out in stages (1) and (2) providingan overall excess of heat.
 2. A process as claimed in claim 1, whereinthe urea reactant is selected from the group consisting of solid ureaand concentrated solutions of urea.
 3. A process as claimed in claim 1,wherein the ammonia reactant is selected from consisting of ammonia andliquid ammonia.
 4. A process as claimed in claim 1, wherein the ammoniumpolyphosphate is principally ammonium pyrophosphate and the at least onetreatment with ammonia is carried out at a temperature between 120* and155*C.
 5. A process as claimed in claim 4 wherein the process isoperated under autothermic conditions.
 6. A process as claimed in claim1, wherein the said at least one treatment with ammonia leads to theformation of a product the non-ortho P2O5 content of which is from 50-70percent of its total P2O5 content.
 7. A process as claimed in claim 1,wherein an urea-ammonium polyphosphate based fertilizer is obtained bythe addition, after the crystallization of urea phosphate and subsequentammoniation thereof, of an amount of urea leading to the production of asolid binary fertilizer containing about 3% N and 30% P2O5.
 8. A processas claimed in claim 7, wherein, by the addition also of potassiumchloride, the product is modified to provide a solid ternary fertilizercontaining about 20% N, 20% P2O5, 20% k2O.
 9. A process as claimed inclaim 1, wherein a liquid fertilizer is obtained by dissolving theurea-ammonium polyphosphate formed in stage (2) in water, whereby aliquid fertilizer containing about 15 to 17% N and 27to 31% P2O5 isprovided.
 10. A process as claimed in claim 1, wherein a liquidfertilizer is obtained by dissolving the urea-ammonium polyphosphateformed in stage (2) in water, and cooling the liquors obtained afterdissolving the urea-ammonium polyphosphate in water to a temperaturelower than 5*C.
 11. A process as claimed in claim 1 wherein a liquidfertilizer is obtained by dissolving the urea-ammonium polyphosphateformed in stage (2) in water and introducing wet process phosphoric acidin the zone in which the urea-ammonium polyphosphate is dissolved.
 12. Aprocess as claimed in claim 10, wherein part of the urea is crystallizedby cooling the urea-ammonium polyphosphate liquor to a temperaturebetween -10* and -15*C, and thereafter the urea and the desiredurea-ammonium polyphosphate liquor are separated.
 13. A process asclaimed in claim 1, wherein the mother liquors left upon the separationof the urea phosphate crystals are concentrated and ammoniated, wherebythe paste is obtained, and a solid binary fertilizer substantiallycontaining 22-25% N and 35.5-36.5% P2O5 is produced by the granulationof material comprising the paste.